How to I get rid of these dots?
What you are seeing are called fireflies.the fireflies are often caused by there not being enough samples for cycles to render with. I recommend upping the sample size you are currently working with.

There is also a really good article on other suggestions which you can try to reduce the noise.

7 Ways to get rid of fireflies

Additionally if all else fails you can also use the despeckle node which is used to smooth areas of an image in which noise is noticeable, while leaving complex areas untouched.

This works by the standard deviation of each pixel and its neighbors is calculated to determine if the area is one of high complexity or low complexity. If the complexity is lower than the threshold then the area is smoothed using a simple mean filter.

This will reduce the quality of your overall scene if your samples are too low however.

Despeckle Node